Rules and methods for insuring safe structural strength of racing airplanes used in the major air meets in this country have recently been considered. Acceleration records made in racing airplanes during actual air races were therefore considered desirable, and the NACA undertook the measurement of acceleration of loads on airplanes during all conditions of flight. Accelerations were measured on four airplanes at the Miami All-American Races in January 1934 and January 1935. The airplanes were representative of the fastest limited and unlimited displacement racing airplanes in current use in this country. Records during two races, or flights, on the race course were obtained with each airplane. The maximum normal acceleration recorded was 6...